1. Field of the Invention
The present invention is generally directed to medical catheters, and specifically directed to a variable diameter catheter (VDC) in which the diameter of the catheter is decreased for insertion into a body cavity.
2. Description of Prior Art
Catheters are ubiquitous to the medical field, finding importance in a variety of uses. The term "catheter" is commonly used to identify a tubular instrument that is inserted into a body cavity or orifice, naturally or surgically opened, and the catheter of the present invention will be understood as intended thus broadly unless the context clearly indicates the contrary. The following list indicates the broad range of uses for catheters:
1. intravenous cannula PA1 2. umbilical catheters PA1 3. endotracheal tubes PA1 4. suction catheters PA1 5. oxygen catheters PA1 6. stomach tubes PA1 7. feeding tubes PA1 8. lavage tubes PA1 9. rectal tubes PA1 10. urological tubes PA1 11. irrigation tubes PA1 12. trocar catheters PA1 13. heart catheters PA1 14. aneurysm shunts PA1 15. stenosis dilators
A history of catheters is presented in parent application Ser. No. 743,705 now U.S. Pat. No. 4,601,713 to Fuqua, which has been incorporated herein by reference, and will not be duplicated in this application. It will suffice to summarize that the present technology relating to catheterization is documented to be the cause of many infection-related problems associated in the medical industry. However, it is still considered to be the lesser of two evils. On the one hand, if the physician does not catheterize a patient, the patient may develop or experience further medical difficulties. On the other hand because catheters are readily available and very common, a physician will undoubtedly insert a catheter and risk the resulting infection.
My parent application Ser. No. 743,705 now U.S. Pat. No. 4,601,713 describes a method and apparatus for producing and using a variable diameter catheter in which the diameter of the catheter is reduced by about one-half for insertion into a body orifice with a minimum of discomfort and difficulty. The wall of the catheter is longitudinally folded upon itself or involuted in order to reduce the overall diameter of the catheter for insertion. The reduced-diameter catheter is held in place by a retaining means placed in the lumen of the catheter.
Until the present invention was developed, it was not thought possible to provide a variable diameter catheter with an external retaining means. At best, the prior art appears to disclose catheters with external housings serving a variety of purposes generally unrelated to the present invention.
For example, U.S. Pat. No. 4,401,433 to Luther is directed to longitudinally folding an oversized catheter by introducing it in a folded state into a cannula. The wall of the catheter does not vary in thickness. The cannula then penetrates a vein and the catheter is inserted into the vein in folded condition. Due to the resiliency of the catheter, the catheter expands into its normal shape as it leaves the cannula. The cannula is then retracted. U.S. Pat. No. 4,411,655 to Schreck discloses the introduction of a reduced diameter catheter. The catheter comprises a "shape memory alloy" which allows the catheter to be at a reduced diameter at one temperature and at a larger diameter at another higher temperature. The catheter is surrounded by a protective sheath. However, there is no fold in the catheter, nor is the sheath removable. U.S. Pat. No. 3,877,429 to Rasumoff is directed to a catheter placement device which is a flexible cannula stiff enough to provide structural support during placement of the catheter. In this case the cannula is first inserted into the blood vessel, and then the catheter is threaded through the cannula causing the cannula to split. The cannula is then withdrawn leaving the catheter in place.
Other patents show sheaths surrounding a catheter in one form or another. For example, Canadian Patent 1,001,034 to McWhorter discloses a suprapubic catheter and a hollow-needle combination. In its natural state, i.e., in the bladder, the catheter is coiled. The hollow needle is meant to introduce the catheter into the bladder. The needle straightens the catheter out but, due to the catheter memory, the coil is regained once the catheter leaves the needle and enters the bladder.
European Patent Application Publication No. 86,338 to Wonder et al is directed to a flexible inner catheter tube which is slidably positioned within a more rigid, outer catheter sheath tube. The sheath gives rigidity to the catheter during the insertion of the catheter into a body orifice. The outer sheath is then retracted after insertion of the catheter at the injection site. Thus, the outer sheath never actually enters the body orifice.
U.S. Pat. No. 4,000,739 to Stevens discloses a hemostasis catheter. The catheter includes a hollow plastic dilator which is slipped over a guide. A hole in the vessel wall is dilated and a tube inside the dilator enters the lumen of the blood vessel. The dilator and guide are then removed and the catheter is inserted into the vessel. PG,6
U.S. Pat. No. 4,564,014 to Fogarty et al discloses a dilation catheter with a telescopic sheath to expose varying lengths of the catheter for inflation.
U.S. Pat. No. 4,573,981 to McFarlane discloses a catheter and protective sheath which prevents damage to the catheter. The sheath is removed prior to insertion of the catheter.
U.S. Pat. No. 3,598,127 to Wepsic discloses a catheter which provides an antibacterial substance throughout the length of the tube. The catheter has an inner tube of nonpermeable rubber formed with V-grooves along the length of the outside of the tube. The grooves carry the antibacterial substance. A permeable polysiloxane rubber sheath surrounds the grooves in order to allow diffusion of the medicine.
U.S. Pat. No. 4,498,902 to Ash et al discloses a catheter guide which is placed in the body through a trocar. The catheter is then introduced through the guide.
U.S. Pat. No. 4,563,176 to Gustavsson et al discloses a protective sheath and catheter. The protective sheath is a plastic bag providing a sterile environment for the catheter.
U.S. Pat. No. 4,327,735 to Hampson discloses a catheter in a collapsible protective sheath. As the catheter enters the body, the sleeve collapses outside the body in accordian-like pleats. The catheter is withdrawn inside the sleeve.
Although some catheter protector sheaths are disclosed in the prior art, it would be advantageous to provide a catheter which has a reduced diameter for insertion into a body orifice and which is provided with a means for both maintaining the reduced diameter and aiding the spread of an anti-infection medicament around the catheter.